Twig will always use gettext, legacy will use legacy. Twig does not
work with legacy so new ui would break if you would not also set this
option. Instead, just switch the system in use based on the usenewui
config variable.

Update config.php
Update header.php

getString doesn't like booleans

This is minor, but if a comma is required when this is enabled the template should reflect that.

Trailing slash is no longer required in baseurlpath as per 1.15.

This can be used by templates to load resources in different ways, either optimized for the developer or for a production environment.

This allows us to use this new filter to translate strings from a given array of translations, where every translation is indexed by its ISO 639 code. A new configuration option ('language' -> 'priorities') is available too to control the alternative languages that can be used instead of a given language, when the latter is not found. The filter returns null when no suitable translation is found, so that it can be combined with "default()" to set a default translation for a given string.

I may be missing something but I haven't found a way to add the --ssl-ca
MySQL option to my database connection. It appears we just need to pass
in an $options param.

The default values are fine if no other applications use PHP sessions. However, when other apps are using PHP sessions, a conflict arises with the defaults, so let's try to make the defaults a bit more resilient.

Frequently people put fs paths in baseurlpath or URL paths in
the other settings. By more clearly separating these two classes
of options I hope to reduce confusion a bit.

`core:ScopeFromAttribute` is a generalised version of this.

Closes: #512

Also add some docs.

Some things, like logging of SAML messages or backtraces, are controlled with the 'debug' configuration option. However, it might be possible that we don't want one while we want the other, but that's impossible with just one option.

This commit allows us to configure debugging options independently, but groupping all of them together. This is particularly useful if we want to log backtraces to debug errors, for example, but we don't want to log SAML messages to keep the privacy of the users. This also allows us to get rid of the 'debug.validatexml' configuration option, and group it with other debug options.

This changes are backwards-compatible. Old and new configurations will work at the same time.

Add the existing Afrikaans translation into the list of supported languages so that South African users don't need to go editing code.

Add a configuration option named 'admin.checkforupdates' to enable or disable this feature.

Update the documentation. Trailing slashes are no longer required for 'baseurlpath'. This resolves #363.

Fixes #379